Vacuum最新文献

Non-evaporable getter (NEG) is widely used in vacuum packaging. However, there are two main contradictions. Firstly, the contradiction between bonding temperature of the device and activation temperature of the getter results in the getter being activated first and then packaged, and cannot be repeatedly activated, which seriously reduces the adsorption capacity and life of the getter. Secondly, the contradiction between the small package volume and the large adsorption capacity, how to integrate large adsorption capacity getter in a small space is a tricky problem. In view of the above contradictions, a porous scaffold-based getter activated by induction heating was proposed in this paper, results show that when nickel plating is used as the induction heating layer, the temperature can quickly rise to 700 °C within 10 s, and 1 μm Ti getter can be fully activated for 7 min. The good periodicity of the temperature curves proved that the nickel layer has good repeatable heating characteristics. In addition, the adsorption performance of the getter was tested and characterized at device level. The device level characterization of optical deflection method proves the effectiveness of induction heating to activate getter, which lays a foundation for the application of getter on MEMS devices.

Using scanning and transmission electron microscopy, X-ray diffraction, profilometry, indentation and friction tests we investigated the microstructure and phase composition formation in the near-surface layer, microhardness, surface roughness, resistance to cracking and wear resistance in Ni₃Al intermetallic compound and “Ni₃Al base – thin powder TiC coating” system processed with low-energy high-current electron beam (LEHCEB). We revealed the crucial role of TiC particles in different behavior of these materials under LEHCEB irradiation with the surface energy density of 8 J/cm², accelerating voltage of 30 kV and 10 pulses. The mass fraction of TiC in the near-surface was as much as 22 wt % after three times surfacing. It was found that the presence of TiC thin layer enabled essential microstructure and phase refinement in the near-surface layer of the surface composites and improvement in microhardness and wear resistance. The density of surface cracks in the surface composites is 1.8 lower with respect to TiC-free Ni₃Al and the roughness keeps the same. The advantages of LEHCEB processing of intermetallic compounds with thin powder layers are attractive for possible practical application.

The high values of bolt preload force $F_a$ = 90–1200 kN created by the ITER remote handling system can be achieved by using dry coating lubricants such as magnetron sputtering film MoS₂ or WS₂. An expression was determined to estimate the contact pressure based on the number thread turns and the width of the thread contact area in fastened assemblies that used the Spiralock technology. This study investigated the tribological aspects of the magnetron sputtering MoS₂ coating at different thicknesses $h_c$ = 6.4–21 μm, contact pressures $p_a$ = 20–1200 MPa against the spherical pin (austenitic stainless steel 316L(N)-IG) at elevated temperatures of $T$ = 250 °C in vacuum $p_v$ = 10⁻²–10⁻³ Pa. Friction data for “humid” and “dry” rectangular specimens with MoS₂ coating were obtained and compared. With an increase in the thickness of the coating from 6.4 μm to 21 μm, we obtained a distinct stabilization the friction coefficient of the low friction coating for each given regime of wear that diminished from 0.09 ± 0.010 to 0.05 ± 0.005. The wear mechanism of the “layered MoS₂ coating/metal substrate” tribosystem resulted in significant plastic deformation along the sliding direction of the MoS₂ solid lubricant as well as microgrooving and microploughing of the coating by the asperities of the flat contact spot of the spherical pin. Regardless of the type of bolted pair alloys used, we concluded that it is necessary to deposit a low friction coating on both the internal and external threads of the ITER blanket module bolted joints that use the Spiralock technology.

Nickel thin films were deposited to the different thicknesses onto glass substrates using electron-beam glancing angle deposition. The changes in the structural, chemical, and magnetic properties of the films have been investigated. The obtained morphological and microstructural results revealed that the deposited samples consisted of vertical columns with a thickness in the range of 50 nm to 140 nm and a diameter of 15 nm to 29 nm. With the increase in film thickness, the surface roughness increases as well. Chemical analysis showed that the main phase in the samples is metallic Ni, with a certain amount of NiO. In addition, magnetic measurements exhibit that all Ni films show typical hysteresis loops with a uniaxial magnetic anisotropy. The coercivity was found to increase with the thickness up to 110 nm followed by its further decrease, probably due to the differences in the structure of the columns themselves as well as the combined contributions of two different antiferromagnetic (NiO) and ferromagnetic (Ni) phases created in the deposited nanostructures.

The formation and destruction of the passivation film on AZ41 Mg alloy embedded in Portland cement paste were investigated via electrochemical methods and surface characterizations. Results indicate a thin but dense passivation film can be formed on the Mg alloy surface, while a distinctive sandwich-like structure of passivation film is observed on the Al-Mn phase. However, Cl⁻ ions could lead to the destruction of the passivation film, resulting in the formation of a corrosion product layer even in the alkaline environment. Moreover, corrosion resistance of AZ41 Mg alloy embedded in Portland cement paste improves over time, while the introduction of chloride ions triggers a decline in corrosion resistance.

In this work, the photothermal effect of aminomodified MWCNTs/TiO₂/SiO₂/PDMS nanocomposites was utilized as a photothermal substrate to replace the metal heating block of traditional qPCR combining of the advantages of high photothermal effect of composite materials and low sample volume of static microfluidic PCR. Meanwhile, Multiple PCR rapid thermal cycles under 808 nm laser irradiation was accomplished through a non-contact energy conversion method and the use of chamber-immobilized PCR chips as specific reaction vessels. Notably, the chip chamber architecture requires merely about 8 μL of reagents compared to traditional PCR tubes. While reducing the amount of PCR reagents used, the higher specific surface area results in a larger contact surface (SSA) between the heat source and the solution. Thereafter, the CCD image sensor is then used as a fluorescence detector to monitor the amplification of the target DNA during the PCR reaction, thus enabling simultaneous fluorescence detection. In addition, the threshold cycle (Ct) value of qPCR and standard PCR curves for SARS-CoV-2 virus have been analysed in depth. Importantly, this study has important implications for the development of low-cost materials, miniaturized and portable Point-of-Care Testing (POCT) chips/systems.

The γ-TiAl alloy is highly regarded as one of the most promising materials in the aerospace industry. Nonetheless, pore defects are an unavoidable challenge during its manufacturing process. To thoroughly examine the impact of these defects on the surface damage mechanism during the nanometric cutting of γ-TiAl alloy, this study utilizes molecular dynamics (MD) simulations to analyze the nanometric cutting of single-crystal γ-TiAl alloy containing pore defects. The research explores the influence of various cutting parameters and pore defect radii on cutting forces, atomic migration and surface morphology, stress and strain, sub-surface defect evolution and atomic phase transformation, and dislocation dynamics, with the goal of clarifying the surface damage mechanisms in nanometric cutting.The findings indicate that as the pore defect radius increases, the disparity between Fx and Fz becomes more pronounced, the Von Mises stress within the chip decreases, and the thickness of the sub-surface defect structure layer diminishes. When the pore defect radius is 15 Å, a "shear-off" phenomenon is observed on the cutting surface, with Fx values ranging from 2.5 to 7 times those of Fz. An increase in cutting depth results in a broader side flow width of the surface chip, raising the proportion of atoms from layers without pore defects within the chip. At a cutting depth of 20 Å, the matrix with larger pore defects shows a distinct strain distribution profile. The atomic structure of the matrix primarily consists of FCC-structured atoms.At high cutting speeds, when the pore defect radius is 10 Å, an increase in cutting depth from 10 Å to 30 Å leads to a 7.9 % rise in amorphous structure atoms. During the cutting process, dislocations predominantly occur in the shear slip zone and near the pore defects. At a cutting speed of 50 m/s and a cutting depth of 10 Å, the density of 1/6<112>(Shockley) dislocations for a pore defect size of 15 Å is 2.24 times that of a 10 Å defect; at a cutting depth of 30 Å, the density of 1/6<112>(Shockley) dislocations for a 10 Å pore defect is 2.15 times that of a 15 Å defect.

Aqueous rechargeable zinc metal batteries have garnered widespread attention due to their inherent high safety, high volumetric capacity, and low cost. However, the uncontrollable growth of zinc dendrites and severe hydrogen evolution reaction (HER) side reactions lead to low Coulombic efficiency and short lifespan of zinc metal anodes, hindering their practical application. We employed a plasma fluorination strategy to in-situ react on the surface of zinc metal to generate an electron-insulating ZnF₂ coating, which reduces HER, suppresses dendrite growth, and enhances the wettability of the electrode with the electrolyte. Through density functional theory (DFT) and molecular dynamics (MD) simulations, we systematically studied the mechanism by which ZnF₂ improves interfacial properties, suppresses the hydrogen evolution reaction (HER), and inhibits dendrite formation. Ultimately, symmetric batteries and Zn@ZnF₂||Cu batteries assembled with Zn@ZnF₂ electrodes exhibited significantly extended cycle life and high Coulombic efficiency. Full cells of Zn@ZnF₂||MnO₂@CNT achieved a cycle life of over 5000 cycles at a current density of 1 A g⁻¹. This study provides a practical method for industrial treatment of the Zn surface and offers an in-depth analysis and discussion of the role of ZnF₂ in inhibiting dendrite growth, HER, and improving interfacial wettability in zinc-ion batteries.

The structure transition of metallic melt strongly depends on temperature and significantly influences the comprehensive properties. However, observing the structure change in experiments is still challenging. Here, molecular dynamics is used to study the melting process and microstructural evolution in single crystal and polycrystal cobalt (Co). The results indicate that the melting process of single crystal structure starts from 1870 K and lasts for a very short period, while the polycrystal melts from about 1760 to 1870 K. In polycrystal Co, the melting initially occurs in grain boundaries, and the melting temperature shows a positive correlation with grain size. An interesting solidification phenomenon occurs on the surface of big grains in the beginning of melting process. The coordination number increasing from 12 to about 13.4 near melting point proves the local expansion of the first coordination shell, indicating the structural evolution from long-range order to short-range order in the continuous heating process. The common neighbor sub-cluster index and Voronoi polyhedron demonstrate the short-range icosahedron structures, while these polyhedrons become polydisperse and isolated in Co liquid. The findings ignite the investigation of the liquid structure origin of crystal materials and extend the understanding of the atomic structure evolution in melting.

The performance upgrading of iron and nitrogen co-doped carbon (Fe-N-C) for peroxymonosulfate (PMS) activation towards contaminants removal and elucidation of the activation mechanism still remains a challenge. In this study, novel iron and nitrogen co-doped carbon (Fe-N-C) catalysts are fabricated through pyrolysis of Fe-modified zeolitic imidazolate framework-8 (ZIF-8) nanocrystals. Catalytic experiments prove that synergistic effects of FeN_x and α/γ-Fe species can boost peroxymonosulfate activation and pollutants degradation. Density functional theory simulations disclose that α/γ-Fe species can optimize the d-band center of FeN_x and adsorption energy for PMS activation, and thus achieve the enhanced catalytic activities for degradation process. Mechanism studies testify that Fe-N-C-PMS* complex and ¹O₂ are main contributors for the catalytic process. This work paves a new way for elaborate design of high-performance Fe-N-C materials and understanding about the non-radical mechanism during environmental applications.